Fundecitrus survey shows reduction in citrus canker in the citrus belt

Citrus canker is present in 10,76% of orange trees in the citrus belt of São Paulo and Triângulo/Southwest Mineiro, which corresponds to 21 million plants, according to the latest survey carried out by Fundecitrus and released at the end of 2021. Contrary the increasing trend of previous years, there was a reduction of 38% compared to the previous year.

“As the occurrence of rain accompanied by wind is the main way of spreading the bacteria that causes citrus canker, the reduction in the disease was already expected due to the unfavorable climate and intense drought in the belt since 2020”, explains Fundecitrus researcher Franklin Behlau .

Low incidences do not negate the presence of the disease and premature fruit drop

Despite the reduction in incidence, citrus canker continues to be present throughout the citrus belt.

The regions with the highest incidences are Votuporanga (45,78%) and São José do Rio Preto (37,99%), while the lowest incidences are in the regions of Altinópolis (0,43%), Itapetininga (1,53%) and Porto Ferreira (1,28%) – however, despite the low rates, Itapetininga and Porto Ferreira were the only regions with an increase in the disease in 2021.

The incidence was also higher on smaller properties: 28,64% of plots and 21,21% of diseased trees on properties with up to 10 thousand trees, while on properties with more than 200 thousand trees these rates were 13,24% and 9,10 ,XNUMX%, respectively.

The survey also showed that plants aged 3 to 5 years are the most affected, with 22,33% of plots and 17,48% of trees suffering from the disease – while in other age groups the values ​​are lower and similar. .

The rate of premature fruit drop due to citrus canker remained stable compared to the previous year. In the 2020/2021 harvest, the disease was responsible for 0,37% of fruit loss before harvest. This was due to the fact that this index considers fruits that were infected by the citrus canker bacteria in the spring-summer of 2019/2020, when the fruits were susceptible and the favorability and disease rates were higher than in 2021.

See the full report: https://www.fundecitrus.com.br/pdf/levantamentos/Relatorio_levantamento_de_doencas_2021-greening_CVC_e_cancro_citrico.pdf.

Rainy periods require attention to proper management

The lower prevalence of citrus canker in orchards in recent months does not indicate that producers can relax in their disease management measures, warns Behlau. “It is likely that citrus canker will continue to be present on properties and that, during the rainy season, new infections will occur if the orchard is not adequately protected”, he adds.

The critical period for the disease to occur is during spring and summer. Therefore, it is important to protect orchards in production and in formation with applications of copper-based products in a volume of spray suitable for each situation. “Today, it is possible to neutralize or minimize losses due to citrus canker by using less copper and water in applications, which must be carried out during a defined period for greater efficiency in protecting fruits”, explains Behlau.

To protect orchards in production, the protection of fruits with copper must occur for up to 120 days after the petals fall or until the orange fruits are 50 millimeters in diameter, that is, throughout spring and early summer. After this phase, the fruits are resistant and the number of applications can be reduced with the aim only of protecting the shoots. In orchards with multiple blooms, fruit protection must continue throughout the summer until the end of the rainy season, in March or April.

For orchards in formation, applications must also be carried out during spring and summer at intervals of 14 to 21 days or whenever there are sprouts.

The most efficient products are fixed copper-based bactericides such as copper hydroxide, cuprous oxide and copper oxychloride, which are the most efficient for controlling citrus canker. The volume of spray can be defined based on the volume of plant crowns – it is recommended to apply 40 to 70 mL/m³ of crown at a working speed of 4,5 to 5,5 km/h.

In young orchards, 30 to 40 mg of metallic copper/m³ of canopy are used, at intervals of 14 or 21 days, respectively. In adult orchards, doses do not need to exceed 0,7 or 1 kg of metallic copper/ha for these intervals.